drivers/virtio/virtio_balloon.c

   1 /*
   2  * Virtio balloon implementation, inspired by Dor Laor and Marcelo
   3  * Tosatti's implementations.
   4  *
   5  *  Copyright 2008 Rusty Russell IBM Corporation
   6  *
   7  *  This program is free software; you can redistribute it and/or modify
   8  *  it under the terms of the GNU General Public License as published by
   9  *  the Free Software Foundation; either version 2 of the License, or
  10  *  (at your option) any later version.
  11  *
  12  *  This program is distributed in the hope that it will be useful,
  13  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  *  GNU General Public License for more details.
  16  *
  17  *  You should have received a copy of the GNU General Public License
  18  *  along with this program; if not, write to the Free Software
  19  *  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
  20  */
  21
  22 #include <linux/virtio.h>
  23 #include <linux/virtio_balloon.h>
  24 #include <linux/swap.h>
  25 #include <linux/kthread.h>
  26 #include <linux/freezer.h>
  27 #include <linux/delay.h>
  28 #include <linux/slab.h>
  29 #include <linux/module.h>
  30 #include <linux/balloon_compaction.h>
  31 #include <linux/oom.h>
  32 #include <linux/wait.h>
  33
  34 /*
  35  * Balloon device works in 4K page units.  So each page is pointed to by
  36  * multiple balloon pages.  All memory counters in this driver are in balloon
  37  * page units.
  38  */
  39 #define VIRTIO_BALLOON_PAGES_PER_PAGE (unsigned)(PAGE_SIZE >> VIRTIO_BALLOON_PFN_SHIFT)
  40 #define VIRTIO_BALLOON_ARRAY_PFNS_MAX 256
  41 #define OOM_VBALLOON_DEFAULT_PAGES 256
  42 #define VIRTBALLOON_OOM_NOTIFY_PRIORITY 80
  43
  44 static int oom_pages = OOM_VBALLOON_DEFAULT_PAGES;
  45 module_param(oom_pages, int, S_IRUSR | S_IWUSR);
  46 MODULE_PARM_DESC(oom_pages, "pages to free on OOM");
  47
  48 struct virtio_balloon {
  49         struct virtio_device *vdev;
  50         struct virtqueue *inflate_vq, *deflate_vq, *stats_vq;
  51
  52         /* Where the ballooning thread waits for config to change. */
  53         wait_queue_head_t config_change;
  54
  55         /* The thread servicing the balloon. */
  56         struct task_struct *thread;
  57
  58         /* Waiting for host to ack the pages we released. */
  59         wait_queue_head_t acked;
  60
  61         /* Number of balloon pages we've told the Host we're not using. */
  62         unsigned int num_pages;
  63         /*
  64          * The pages we've told the Host we're not using are enqueued
  65          * at vb_dev_info->pages list.
  66          * Each page on this list adds VIRTIO_BALLOON_PAGES_PER_PAGE
  67          * to num_pages above.
  68          */
  69         struct balloon_dev_info vb_dev_info;
  70
  71         /* Synchronize access/update to this struct virtio_balloon elements */
  72         struct mutex balloon_lock;
  73
  74         /* The array of pfns we tell the Host about. */
  75         unsigned int num_pfns;
  76         u32 pfns[VIRTIO_BALLOON_ARRAY_PFNS_MAX];
  77
  78         /* Memory statistics */
  79         int need_stats_update;
  80         struct virtio_balloon_stat stats[VIRTIO_BALLOON_S_NR];
  81
  82         /* To register callback in oom notifier call chain */
  83         struct notifier_block nb;
  84 };
  85
  86 static struct virtio_device_id id_table[] = {
  87         { VIRTIO_ID_BALLOON, VIRTIO_DEV_ANY_ID },
  88         { 0 },
  89 };
  90
  91 static u32 page_to_balloon_pfn(struct page *page)
  92 {
  93         unsigned long pfn = page_to_pfn(page);
  94
  95         BUILD_BUG_ON(PAGE_SHIFT < VIRTIO_BALLOON_PFN_SHIFT);
  96         /* Convert pfn from Linux page size to balloon page size. */
  97         return pfn * VIRTIO_BALLOON_PAGES_PER_PAGE;
  98 }
  99
 100 static struct page *balloon_pfn_to_page(u32 pfn)
 101 {
 102         BUG_ON(pfn % VIRTIO_BALLOON_PAGES_PER_PAGE);
 103         return pfn_to_page(pfn / VIRTIO_BALLOON_PAGES_PER_PAGE);
 104 }
 105
 106 static void balloon_ack(struct virtqueue *vq)
 107 {
 108         struct virtio_balloon *vb = vq->vdev->priv;
 109
 110         wake_up(&vb->acked);
 111 }
 112
 113 static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq)
 114 {
 115         struct scatterlist sg;
 116         unsigned int len;
 117
 118         sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns);
 119
 120         /* We should always be able to add one buffer to an empty queue. */
 121         virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL);
 122         virtqueue_kick(vq);
 123
 124         /* When host has read buffer, this completes via balloon_ack */
 125         wait_event(vb->acked, virtqueue_get_buf(vq, &len));
 126 }
 127
 128 static void set_page_pfns(u32 pfns[], struct page *page)
 129 {
 130         unsigned int i;
 131
 132         /* Set balloon pfns pointing at this page.
 133          * Note that the first pfn points at start of the page. */
 134         for (i = 0; i < VIRTIO_BALLOON_PAGES_PER_PAGE; i++)
 135                 pfns[i] = page_to_balloon_pfn(page) + i;
 136 }
 137
 138 static void fill_balloon(struct virtio_balloon *vb, size_t num)
 139 {
 140         struct balloon_dev_info *vb_dev_info = &vb->vb_dev_info;
 141
 142         /* We can only do one array worth at a time. */
 143         num = min(num, ARRAY_SIZE(vb->pfns));
 144
 145         mutex_lock(&vb->balloon_lock);
 146         for (vb->num_pfns = 0; vb->num_pfns < num;
 147              vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
 148                 struct page *page = balloon_page_enqueue(vb_dev_info);
 149
 150                 if (!page) {
 151                         dev_info_ratelimited(&vb->vdev->dev,
 152                                              "Out of puff! Can't get %u pages\n",
 153                                              VIRTIO_BALLOON_PAGES_PER_PAGE);
 154                         /* Sleep for at least 1/5 of a second before retry. */
 155                         msleep(200);
 156                         break;
 157                 }
 158                 set_page_pfns(vb->pfns + vb->num_pfns, page);
 159                 vb->num_pages += VIRTIO_BALLOON_PAGES_PER_PAGE;
 160                 if (!virtio_has_feature(vb->vdev,
 161                                         VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
 162                         adjust_managed_page_count(page, -1);
 163         }
 164
 165         /* Did we get any? */
 166         if (vb->num_pfns != 0)
 167                 tell_host(vb, vb->inflate_vq);
 168         mutex_unlock(&vb->balloon_lock);
 169 }
 170
 171 static void release_pages_balloon(struct virtio_balloon *vb)
 172 {
 173         unsigned int i;
 174
 175         /* Find pfns pointing at start of each page, get pages and free them. */
 176         for (i = 0; i < vb->num_pfns; i += VIRTIO_BALLOON_PAGES_PER_PAGE) {
 177                 struct page *page = balloon_pfn_to_page(vb->pfns[i]);
 178                 if (!virtio_has_feature(vb->vdev,
 179                                         VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
 180                         adjust_managed_page_count(page, 1);
 181                 put_page(page); /* balloon reference */
 182         }
 183 }
 184
 185 static unsigned leak_balloon(struct virtio_balloon *vb, size_t num)
 186 {
 187         unsigned num_freed_pages;
 188         struct page *page;
 189         struct balloon_dev_info *vb_dev_info = &vb->vb_dev_info;
 190
 191         /* We can only do one array worth at a time. */
 192         num = min(num, ARRAY_SIZE(vb->pfns));
 193
 194         mutex_lock(&vb->balloon_lock);
 195         for (vb->num_pfns = 0; vb->num_pfns < num;
 196              vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
 197                 page = balloon_page_dequeue(vb_dev_info);
 198                 if (!page)
 199                         break;
 200                 set_page_pfns(vb->pfns + vb->num_pfns, page);
 201                 vb->num_pages -= VIRTIO_BALLOON_PAGES_PER_PAGE;
 202         }
 203
 204         num_freed_pages = vb->num_pfns;
 205         /*
 206          * Note that if
 207          * virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST);
 208          * is true, we *have* to do it in this order
 209          */
 210         if (vb->num_pfns != 0)
 211                 tell_host(vb, vb->deflate_vq);
 212         mutex_unlock(&vb->balloon_lock);
 213         release_pages_balloon(vb);
 214         return num_freed_pages;
 215 }
 216
 217 static inline void update_stat(struct virtio_balloon *vb, int idx,
 218                                u16 tag, u64 val)
 219 {
 220         BUG_ON(idx >= VIRTIO_BALLOON_S_NR);
 221         vb->stats[idx].tag = cpu_to_virtio16(vb->vdev, tag);
 222         vb->stats[idx].val = cpu_to_virtio64(vb->vdev, val);
 223 }
 224
 225 #define pages_to_bytes(x) ((u64)(x) << PAGE_SHIFT)
 226
 227 static void update_balloon_stats(struct virtio_balloon *vb)
 228 {
 229         unsigned long events[NR_VM_EVENT_ITEMS];
 230         struct sysinfo i;
 231         int idx = 0;
 232
 233         all_vm_events(events);
 234         si_meminfo(&i);
 235
 236         update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_IN,
 237                                 pages_to_bytes(events[PSWPIN]));
 238         update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_OUT,
 239                                 pages_to_bytes(events[PSWPOUT]));
 240         update_stat(vb, idx++, VIRTIO_BALLOON_S_MAJFLT, events[PGMAJFAULT]);
 241         update_stat(vb, idx++, VIRTIO_BALLOON_S_MINFLT, events[PGFAULT]);
 242         update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMFREE,
 243                                 pages_to_bytes(i.freeram));
 244         update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMTOT,
 245                                 pages_to_bytes(i.totalram));
 246 }
 247
 248 /*
 249  * While most virtqueues communicate guest-initiated requests to the hypervisor,
 250  * the stats queue operates in reverse.  The driver initializes the virtqueue
 251  * with a single buffer.  From that point forward, all conversations consist of
 252  * a hypervisor request (a call to this function) which directs us to refill
 253  * the virtqueue with a fresh stats buffer.  Since stats collection can sleep,
 254  * we notify our kthread which does the actual work via stats_handle_request().
 255  */
 256 static void stats_request(struct virtqueue *vq)
 257 {
 258         struct virtio_balloon *vb = vq->vdev->priv;
 259
 260         vb->need_stats_update = 1;
 261         wake_up(&vb->config_change);
 262 }
 263
 264 static void stats_handle_request(struct virtio_balloon *vb)
 265 {
 266         struct virtqueue *vq;
 267         struct scatterlist sg;
 268         unsigned int len;
 269
 270         vb->need_stats_update = 0;
 271         update_balloon_stats(vb);
 272
 273         vq = vb->stats_vq;
 274         if (!virtqueue_get_buf(vq, &len))
 275                 return;
 276         sg_init_one(&sg, vb->stats, sizeof(vb->stats));
 277         virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL);
 278         virtqueue_kick(vq);
 279 }
 280
 281 static void virtballoon_changed(struct virtio_device *vdev)
 282 {
 283         struct virtio_balloon *vb = vdev->priv;
 284
 285         wake_up(&vb->config_change);
 286 }
 287
 288 static inline s64 towards_target(struct virtio_balloon *vb)
 289 {
 290         s64 target;
 291         u32 num_pages;
 292
 293         virtio_cread(vb->vdev, struct virtio_balloon_config, num_pages,
 294                      &num_pages);
 295
 296         /* Legacy balloon config space is LE, unlike all other devices. */
 297         if (!virtio_has_feature(vb->vdev, VIRTIO_F_VERSION_1))
 298                 num_pages = le32_to_cpu((__force __le32)num_pages);
 299
 300         target = num_pages;
 301         return target - vb->num_pages;
 302 }
 303
 304 static void update_balloon_size(struct virtio_balloon *vb)
 305 {
 306         u32 actual = vb->num_pages;
 307
 308         /* Legacy balloon config space is LE, unlike all other devices. */
 309         if (!virtio_has_feature(vb->vdev, VIRTIO_F_VERSION_1))
 310                 actual = (__force u32)cpu_to_le32(actual);
 311
 312         virtio_cwrite(vb->vdev, struct virtio_balloon_config, actual,
 313                       &actual);
 314 }
 315
 316 /*
 317  * virtballoon_oom_notify - release pages when system is under severe
 318  *                          memory pressure (called from out_of_memory())
 319  * @self : notifier block struct
 320  * @dummy: not used
 321  * @parm : returned - number of freed pages
 322  *
 323  * The balancing of memory by use of the virtio balloon should not cause
 324  * the termination of processes while there are pages in the balloon.
 325  * If virtio balloon manages to release some memory, it will make the
 326  * system return and retry the allocation that forced the OOM killer
 327  * to run.
 328  */
 329 static int virtballoon_oom_notify(struct notifier_block *self,
 330                                   unsigned long dummy, void *parm)
 331 {
 332         struct virtio_balloon *vb;
 333         unsigned long *freed;
 334         unsigned num_freed_pages;
 335
 336         vb = container_of(self, struct virtio_balloon, nb);
 337         if (!virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
 338                 return NOTIFY_OK;
 339
 340         freed = parm;
 341         num_freed_pages = leak_balloon(vb, oom_pages);
 342         update_balloon_size(vb);
 343         *freed += num_freed_pages;
 344
 345         return NOTIFY_OK;
 346 }
 347
 348 static int balloon(void *_vballoon)
 349 {
 350         struct virtio_balloon *vb = _vballoon;
 351         DEFINE_WAIT_FUNC(wait, woken_wake_function);
 352
 353         set_freezable();
 354         while (!kthread_should_stop()) {
 355                 s64 diff;
 356
 357                 try_to_freeze();
 358
 359                 add_wait_queue(&vb->config_change, &wait);
 360                 for (;;) {
 361                         if ((diff = towards_target(vb)) != 0 ||
 362                             vb->need_stats_update ||
 363                             kthread_should_stop() ||
 364                             freezing(current))
 365                                 break;
 366                         wait_woken(&wait, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
 367                 }
 368                 remove_wait_queue(&vb->config_change, &wait);
 369
 370                 if (vb->need_stats_update)
 371                         stats_handle_request(vb);
 372                 if (diff > 0)
 373                         fill_balloon(vb, diff);
 374                 else if (diff < 0)
 375                         leak_balloon(vb, -diff);
 376                 update_balloon_size(vb);
 377
 378                 /*
 379                  * For large balloon changes, we could spend a lot of time
 380                  * and always have work to do.  Be nice if preempt disabled.
 381                  */
 382                 cond_resched();
 383         }
 384         return 0;
 385 }
 386
 387 static int init_vqs(struct virtio_balloon *vb)
 388 {
 389         struct virtqueue *vqs[3];
 390         vq_callback_t *callbacks[] = { balloon_ack, balloon_ack, stats_request };
 391         const char *names[] = { "inflate", "deflate", "stats" };
 392         int err, nvqs;
 393
 394         /*
 395          * We expect two virtqueues: inflate and deflate, and
 396          * optionally stat.
 397          */
 398         nvqs = virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ) ? 3 : 2;
 399         err = vb->vdev->config->find_vqs(vb->vdev, nvqs, vqs, callbacks, names);
 400         if (err)
 401                 return err;
 402
 403         vb->inflate_vq = vqs[0];
 404         vb->deflate_vq = vqs[1];
 405         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
 406                 struct scatterlist sg;
 407                 vb->stats_vq = vqs[2];
 408
 409                 /*
 410                  * Prime this virtqueue with one buffer so the hypervisor can
 411                  * use it to signal us later (it can't be broken yet!).
 412                  */
 413                 sg_init_one(&sg, vb->stats, sizeof vb->stats);
 414                 if (virtqueue_add_outbuf(vb->stats_vq, &sg, 1, vb, GFP_KERNEL)
 415                     < 0)
 416                         BUG();
 417                 virtqueue_kick(vb->stats_vq);
 418         }
 419         return 0;
 420 }
 421
 422 #ifdef CONFIG_BALLOON_COMPACTION
 423 /*
 424  * virtballoon_migratepage - perform the balloon page migration on behalf of
 425  *                           a compation thread.     (called under page lock)
 426  * @vb_dev_info: the balloon device
 427  * @newpage: page that will replace the isolated page after migration finishes.
 428  * @page   : the isolated (old) page that is about to be migrated to newpage.
 429  * @mode   : compaction mode -- not used for balloon page migration.
 430  *
 431  * After a ballooned page gets isolated by compaction procedures, this is the
 432  * function that performs the page migration on behalf of a compaction thread
 433  * The page migration for virtio balloon is done in a simple swap fashion which
 434  * follows these two macro steps:
 435  *  1) insert newpage into vb->pages list and update the host about it;
 436  *  2) update the host about the old page removed from vb->pages list;
 437  *
 438  * This function preforms the balloon page migration task.
 439  * Called through balloon_mapping->a_ops->migratepage
 440  */
 441 static int virtballoon_migratepage(struct balloon_dev_info *vb_dev_info,
 442                 struct page *newpage, struct page *page, enum migrate_mode mode)
 443 {
 444         struct virtio_balloon *vb = container_of(vb_dev_info,
 445                         struct virtio_balloon, vb_dev_info);
 446         unsigned long flags;
 447
 448         /*
 449          * In order to avoid lock contention while migrating pages concurrently
 450          * to leak_balloon() or fill_balloon() we just give up the balloon_lock
 451          * this turn, as it is easier to retry the page migration later.
 452          * This also prevents fill_balloon() getting stuck into a mutex
 453          * recursion in the case it ends up triggering memory compaction
 454          * while it is attempting to inflate the ballon.
 455          */
 456         if (!mutex_trylock(&vb->balloon_lock))
 457                 return -EAGAIN;
 458
 459         get_page(newpage); /* balloon reference */
 460
 461         /* balloon's page migration 1st step  -- inflate "newpage" */
 462         spin_lock_irqsave(&vb_dev_info->pages_lock, flags);
 463         balloon_page_insert(vb_dev_info, newpage);
 464         vb_dev_info->isolated_pages--;
 465         __count_vm_event(BALLOON_MIGRATE);
 466         spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags);
 467         vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
 468         set_page_pfns(vb->pfns, newpage);
 469         tell_host(vb, vb->inflate_vq);
 470
 471         /* balloon's page migration 2nd step -- deflate "page" */
 472         balloon_page_delete(page);
 473         vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
 474         set_page_pfns(vb->pfns, page);
 475         tell_host(vb, vb->deflate_vq);
 476
 477         mutex_unlock(&vb->balloon_lock);
 478
 479         put_page(page); /* balloon reference */
 480
 481         return MIGRATEPAGE_SUCCESS;
 482 }
 483 #endif /* CONFIG_BALLOON_COMPACTION */
 484
 485 static int virtballoon_probe(struct virtio_device *vdev)
 486 {
 487         struct virtio_balloon *vb;
 488         int err;
 489
 490         if (!vdev->config->get) {
 491                 dev_err(&vdev->dev, "%s failure: config access disabled\n",
 492                         __func__);
 493                 return -EINVAL;
 494         }
 495
 496         vdev->priv = vb = kmalloc(sizeof(*vb), GFP_KERNEL);
 497         if (!vb) {
 498                 err = -ENOMEM;
 499                 goto out;
 500         }
 501
 502         vb->num_pages = 0;
 503         mutex_init(&vb->balloon_lock);
 504         init_waitqueue_head(&vb->config_change);
 505         init_waitqueue_head(&vb->acked);
 506         vb->vdev = vdev;
 507         vb->need_stats_update = 0;
 508
 509         balloon_devinfo_init(&vb->vb_dev_info);
 510 #ifdef CONFIG_BALLOON_COMPACTION
 511         vb->vb_dev_info.migratepage = virtballoon_migratepage;
 512 #endif
 513
 514         err = init_vqs(vb);
 515         if (err)
 516                 goto out_free_vb;
 517
 518         vb->nb.notifier_call = virtballoon_oom_notify;
 519         vb->nb.priority = VIRTBALLOON_OOM_NOTIFY_PRIORITY;
 520         err = register_oom_notifier(&vb->nb);
 521         if (err < 0)
 522                 goto out_oom_notify;
 523
 524         virtio_device_ready(vdev);
 525
 526         vb->thread = kthread_run(balloon, vb, "vballoon");
 527         if (IS_ERR(vb->thread)) {
 528                 err = PTR_ERR(vb->thread);
 529                 goto out_del_vqs;
 530         }
 531
 532         return 0;
 533
 534 out_del_vqs:
 535         unregister_oom_notifier(&vb->nb);
 536 out_oom_notify:
 537         vdev->config->del_vqs(vdev);
 538 out_free_vb:
 539         kfree(vb);
 540 out:
 541         return err;
 542 }
 543
 544 static void remove_common(struct virtio_balloon *vb)
 545 {
 546         /* There might be pages left in the balloon: free them. */
 547         while (vb->num_pages)
 548                 leak_balloon(vb, vb->num_pages);
 549         update_balloon_size(vb);
 550
 551         /* Now we reset the device so we can clean up the queues. */
 552         vb->vdev->config->reset(vb->vdev);
 553
 554         vb->vdev->config->del_vqs(vb->vdev);
 555 }
 556
 557 static void virtballoon_remove(struct virtio_device *vdev)
 558 {
 559         struct virtio_balloon *vb = vdev->priv;
 560
 561         unregister_oom_notifier(&vb->nb);
 562         kthread_stop(vb->thread);
 563         remove_common(vb);
 564         kfree(vb);
 565 }
 566
 567 #ifdef CONFIG_PM_SLEEP
 568 static int virtballoon_freeze(struct virtio_device *vdev)
 569 {
 570         struct virtio_balloon *vb = vdev->priv;
 571
 572         /*
 573          * The kthread is already frozen by the PM core before this
 574          * function is called.
 575          */
 576
 577         remove_common(vb);
 578         return 0;
 579 }
 580
 581 static int virtballoon_restore(struct virtio_device *vdev)
 582 {
 583         struct virtio_balloon *vb = vdev->priv;
 584         int ret;
 585
 586         ret = init_vqs(vdev->priv);
 587         if (ret)
 588                 return ret;
 589
 590         virtio_device_ready(vdev);
 591
 592         fill_balloon(vb, towards_target(vb));
 593         update_balloon_size(vb);
 594         return 0;
 595 }
 596 #endif
 597
 598 static unsigned int features[] = {
 599         VIRTIO_BALLOON_F_MUST_TELL_HOST,
 600         VIRTIO_BALLOON_F_STATS_VQ,
 601         VIRTIO_BALLOON_F_DEFLATE_ON_OOM,
 602 };
 603
 604 static struct virtio_driver virtio_balloon_driver = {
 605         .feature_table = features,
 606         .feature_table_size = ARRAY_SIZE(features),
 607         .driver.name =  KBUILD_MODNAME,
 608         .driver.owner = THIS_MODULE,
 609         .id_table =     id_table,
 610         .probe =        virtballoon_probe,
 611         .remove =       virtballoon_remove,
 612         .config_changed = virtballoon_changed,
 613 #ifdef CONFIG_PM_SLEEP
 614         .freeze =       virtballoon_freeze,
 615         .restore =      virtballoon_restore,
 616 #endif
 617 };
 618
 619 module_virtio_driver(virtio_balloon_driver);
 620 MODULE_DEVICE_TABLE(virtio, id_table);
 621 MODULE_DESCRIPTION("Virtio balloon driver");
 622 MODULE_LICENSE("GPL");